The present invention relates generally to the machining industry and, more particularly, to chucks which are utilized to hold workpieces/stock during the machining process.
In the stock material machining industry there are basically two types of chucks which are used to hold the stock material while it is machined. In a fixed chuck, a plurality of jaws (such as three) move simultaneously and radially inward to contact the outer surface of the stock material. The jaws must always move in unison and therefore always move the same amount. Accordingly, if a piece of stock material such as generally cylindrical stock material is not perfectly cylindrical, all three chuck jaws might not contact the outer surface of the stock material, or even if all three jaws do contact the outer surface of the stock material, the stock material may not be centered properly on the central machining axis of the chuck. With such a fixed chuck, it is therefore necessary to first machine one end of the stock material to form a xe2x80x9cchucking hubxe2x80x9d which is known to be cylindrical about a central axis of the stock material. The jaws of the fixed chuck can then be placed into engagement with the chucking hub of the stock material to hold the stock in a properly aligned manner for rotation and machining.
In a self-adjusting or compensating chuck, the plurality of chuck jaws move radially inwardly in an independent manner so that non-cylindrical or eccentric stock material can be held along its central axis without having to turn a chucking hub. In particular, a center (an indentation) of the stock material is aligned with a mating center (projection) of the self-adjusting chuck and as the jaws move radially inward if one jaw contacts the outer surface of the stock material first, its movement is halted while the other jaws continue to move radially inward until they contact the stock material.
Accordingly, it would be desirable and advantageous to provide a simple mechanism for converting a fixed chuck to a compensating chuck.
In one aspect of the present invention, a chuck adapter attachable to a fixed chuck mechanism for converting the fixed chuck mechanism to a compensating chuck mechanism includes an attachment plate for connection to the head of the fixed chuck mechanism. The attachment plate includes a plurality of slots formed therein for alignment with respective moveable drive jaws on the fixed chuck head. A plurality of adapter jaws are provided, each movable along a respective one of the plate slots, each adapter jaw including a movable clamping pin extending therefrom, and each adapter jaw including a hydraulic displacement member which reacts to movement of the clamping pin. A hydraulic circuit is provided in fluid communication with each of the hydraulic displacement members. Preferably, the hydraulic circuit maintains substantially the same clamping force on each of the clamping pins as the clamping pins move.
In another aspect of the invention, a chuck mechanism includes a fixed chuck head having a plurality of drive jaws which move in unison with each other. A plurality of movable adapter jaws are provided, each adapter jaw in contact with one of the fixed chuck drive jaws for movement therewith. Each adapter jaw includes a movable clamping pin extending therefrom and a hydraulic displacement member which reacts to movement of the clamping pin. A hydraulic circuit is provided in fluid communication with each of the hydraulic displacement members.
Still a further aspect of the invention provides a method for converting a fixed chuck head to a compensating head including the steps of (a) providing a plurality of adapter jaws, each of which includes a base portion and a clamping pin movable relative thereto, where the movement of the clamping pin causes movement of a hydraulic displacement member; (b) providing a hydraulic circuit between the plurality of adapter jaws for providing a hydraulic clamping force on each of the clamping pins via the hydraulic displacement members; and (c) operatively connecting each of the adapter jaws for movement with a respective movable jaw of the fixed chuck.